Energy and material refineries of future: Wastewater treatment plants

There have been many important milestones on humanity's long journey towards achieving environmental sanitation. In particular, the development of the activated sludge system can be claimed to be one of the most groundbreaking advances in the protection of both public health and the wider ecosystem. The first wastewater treatment plants (WWTPs) were developed over a century ago and were soon configured for use with activated sludge. However, despite their long history and service, conventional activated sludge (CAS) plants have become an unsustainable method of wastewater treatment. In addition, conventional WWTPs are intensive energy-consumers and at best allow only very limited material recovery. A paradigm shift to convert existing WWTPs into more sustainable facilities must therefore be considered necessary and to this end the wastewater biorefinery (WWBR) concept may be considered a solution that maximizes both energy and material recovery, in line with the circular economy approach.

The effect of adjustment and finishing procedure on roughness, strength, and phase transformation of monolithic zirconia

OBJECTIVE

To evaluate the effect of adjustment and finishing procedures and thermal aging of monolithic zirconia on the surface roughness, phase transformation, and flexural strength.

MATERIAL AND METHODS

One hundred disk-shaped monolithic zirconia specimens were randomly divided into 5 groups: control, received only glazing; group Gr, was grinded; group GrP, was grinded and polished; group GrG, was grinded and re-glazed; group GrPG, was re-glazed after grinding and polishing. Half of the each group were stored in distilled water for 24 h and the remaining were thermocycled for 5000 cycles. Topographic evaluations were done with profilometer and scanning electron microscope. Phase changes were assessed through X-ray diffractometer. The biaxial flexural strength test was calculated by universal test machine. Statistical analysis was performed by using two-way ANOVA and Tukey multiple comparison test (p < 0.05).

RESULTS

Group Gr showed statistically higher surface roughness and flexural strength values than the other groups (p < 0.001). However, no significant differences were observed between finishing groups (p >0.05). Phase transformation was occurred in all groups but the differences were not statically significant (p >0.05). Artificial aging had no effect on surface roughness, flexural strength, and phase transformation (p >0.05).

CONCLUSION

Surface roughness significantly increased after grinding, but finishing procedure approximated it to the control group. Glazing after grinding decreased the flexural strength, but polishing did not. Zirconia polishing system may be an alternative to re-glazing for monolithic zirconia.

CLINICAL RELEVANCE

Polishing is one of the most effective finishing procedures that can improve the physical properties of the material without damaging its mechanical properties.

Comparative evaluation of cost for preliminary and tertiary municipal wastewater treatment plants in Istanbul

As the global economy continues to grow, the need for an economic evaluation of wastewater treatment plants (WWTPs) is increasing. Determination of cost functions (CFs) helps to assess the costs of WWTP and to be able to reach to the satisfactory financial levels of construction and operation practices in the early phases of a project. In this study, unit capital and operation and maintenance (O&M) costs were calculated by analyzing the real capital and operation and maintenance expenditures of 16 full-scale WWTPs in Istanbul. Besides, the impacts of treatment level and capacity on costs were investigated. The unit total capital cost was found as 0.013 ± 0.004 €/m³ and 0.054 ± 0.009 €/m³ for preliminary and tertiary treatment, respectively, whereas the unit total O&M cost were 0.011 ± 0.007 €/m³ and 0.077 ± 0.021 €/m³ for preliminary and tertiary treatment, respectively. Capital (investment) costs covered 58% of the total cost in preliminary WWTPs, whereas; O&M costs had the highest share (58%) in tertiary WWTPs. The results of this study confirmed that the level of treatment considerably affected the costs of WWTPs. Moreover, the CFs were separately derived for tertiary treatment including A²O with and without digester. The CFs obtained in this study are of utmost importance to be used in the economic evaluation of the planned WWTPs and in the management of existing ones.

Root and canopy traits and adaptability genes explain drought tolerance responses in winter wheat

Bread wheat (Triticum aestivum L) is one of the three main staple crops worldwide contributing 20% calories in the human diet. Drought stress is the main factor limiting yields and threatening food security, with climate change resulting in more frequent and intense drought. Developing drought-tolerant wheat cultivars is a promising way forward. The use of holistic approaches that include high-throughput phenotyping and genetic markers in selection could help in accelerating genetic gains. Fifty advanced breeding lines were selected from the CIMMYT Turkey winter wheat breeding program and studied under irrigated and semiarid conditions in two years. High-throughput phenotyping was done for wheat crown root traits and canopy senescence dynamics using vegetation indices (green area using RGB images and Normalized Difference Vegetation Index using spectral reflectance). In addition, genotyping by KASP markers for adaptability genes was done. Overall, under semiarid conditions yield reduced by 3.09 t ha^-1 (-46.8%) compared to irrigated conditions. Genotypes responded differently under drought stress and genotypes 39 (VORONA/HD24-12//GUN/7/VEE#8//…/8/ALTAY), 18 (BiII98) and 29 (NIKIFOR//KROSHKA) were the most drought tolerant. Root traits including shallow nodal root angle under irrigated conditions and root number per shoot under semiarid conditions were correlated with increased grain yield. RGB based vegetation index measuring canopy green area at anthesis was better correlated with GY than NDVI was with GY under drought. The markers for five established functional genes (PRR73.A1 –flowering time, TEF-7A –grain size and weight, TaCwi.4A - yield under drought, Dreb1- drought tolerance, and ISBW11.GY.QTL.CANDIDATE- grain yield) were associated with different drought-tolerance traits in this experiment. We conclude that–genotypes 39, 18 and 29 could be used for drought tolerance breeding. The trait combinations of canopy green area at anthesis, and root number per shoot along with key drought adaptability makers (TaCwi.4A and Dreb1) could be used in screening drought tolerance wheat breeding lines.

Tear function alterations in patients with polycystic ovary syndrome

OBJECTIVE

Complaints of dry eye are prevalent worldwide and are known to be associated with insulin resistance (IR) and hyperandrogenism. However, dry eye is often overlooked in the context of polycystic ovary syndrome (PCOS). The aim of the present study was to evaluate whether or not there is any relation between tear functions and PCOS, which is a multifaceted disorder associated with IR or hyperandrogenism.

PATIENTS AND METHODS

A total of 35 women with polycystic ovary syndrome (PCOS) were enrolled in this study, along with 27 healthy controls. Body mass index (BMI), follicle-stimulating hormone (FSH), luteinizing hormone (LH) and free testosterone levels on the third day of menstruation were recorded, as well as hirsutism score (using the Ferriman Gallwey scoring system), insulin resistance (homeostasis model assessment), neutrophil-to- lymphocyte ratios (NLR), platelet-to-lymphocyte ratios (PLR), and mean platelet volumes (MPV). A complete ocular examination was followed by administration of the ocular surface disease index (OSDI) questionnaire and Schirmer and tear break-up time (TBUT) tests.

RESULTS

Schirmer and OSDI results were similar between groups, but TBUT was significantly lower in the PCOS group (p = 0.002). There were negative correlations between FG score and TBUT test (r = -0.406, p = 0.001) and between NLR and Schirmer test (r = -0.294, p = 0.025).

CONCLUSIONS

Although subjective dry eye symptoms do not present in all patients, these results confirm that tear reduction, which can cause further complications in patients with PCOS, can be detected by careful examination and sensitive tests.

In vitro effect of moxifloxacin and rifampicin on biofilm formation by clinical MRSA isolates

OBJECTIVE

In this study, it was aimed to investigate in vitro activity of moxifloxacin and rifampicin on biofilm formation by clinical MRSA isolates.

BACKGROUND

Methicillin resistant Staphylococcus aureus (MRSA) strains could be the causative agent in chronical and medical device associated infections by biofilm formation.

METHODS

Moxifloxacin and rifampicin MIC values of 98 MRSA clinical isolates were determined by microdilution method. Biofilm formation of all isolates was determined in 96-well microplates by using spectrophotometric method. Effects of MIC and sub-inhibitory concentrations (1/2 and 1/4 MIC) of antibiotics on biofilm formation were examined in 46 strong biofilm producer strains.

RESULTS

Biofilm production decreased in 37 and 44 isolates at all studied concentrations of moxifloxacin and rifampicin, respectively. Biofilm production increased in six isolates with moxifloxacin and in two isolates with rifampicin.

CONCLUSION

Biofilm inhibitory effect of rifampicin was found to be stronger than moxifloxacin in the examined strains. The studied antimicrobials also induced biofilm formation in some strains. Results of this study may help to evaluate the effects of these antibiotics on biofilm formation of clinical MRSA strains and to control the antibiotic resistance in clinical settings (Tab. 2, Ref. 25).

Confectionery industry: a case study on treatability-based effluent characterization and treatment system performance

Source-based wastewater characterization and stream segregation provide effective management of industrial wastewaters. The characterization of wastewater sources from a confectionery factory was presented and performance of the wastewater treatment plant was evaluated in this study. All of the wastewater sources in the factory, except the vacuum water line, can be characterized by high concentrations of soluble pollutants and low pH. High organic content of the wastewater generated from the confectionery industry promoted the application of anaerobic technology as a pre-treatment before the conventional aerobic treatment. The average chemical oxygen demand (COD) removal and biogas production for expanded granular sludge bed reactor were 88% and 1,730 Nm(3)/day, respectively. The effluent from the investigated facility can be used for irrigation provided that conductivity values are within acceptable limits.

The feasibility of a centralized biogas plant treating the manure produced by an organized animal farmers union in Turkey

The aim of this study is to evaluate the feasibility and the energy recovery potential of mesophilic (30-35 °C) anaerobic digestion of animal wastes (manure) at a centralized biogas plant (CBP) for 35,000 cattle. The proposed CBP is composed of an equalization tank followed by pasteurization and 3+[1/2] modules; i.e. each module consists of four completely mixed anaerobic reactors with a capacity of treating the manure from 10,000 cattle. The effect of maize silage loading, as the co-substrate, both on biomethane production and feasibility of the system was also evaluated. Besides, the transport fuel substitutes of the produced biomethane with or without co-substrate were also investigated. Results of the proposed CBP indicated that biomethane production increased ca. 1.65 fold with co-substrate addition and pay-back periods for one module treating 10,000 cattle manure are calculated to be ca. 11 and 7.0 yr without and with silage addition, respectively. Besides, considering the potential revenue when replacing transport fuels, about 74 heavy goods vehicles or 1,560 cars may be powered per year by the biogas produced from the proposed CBP where the co-digestion of manure and maize silage is applied.

Turner syndrome and 45,X/47,XXX mosaicism

The occurrence of double aneuploidy is a relatively rare phenomenon. We report on a 17-year-old woman with short stature, minimal pubic and axillar hair and short hands. In cultured lymphocyte a double aneuploidy mosaicism was detected, consisting of a cell line with trisomy for X chromosome and a cell line with monosomy for the X-chromosome and no cell line with a normal karyotype. To our knowledge, this is the first case of mosaic 45,X/47,XXX in Turkey.

Effects of fusion angle on functional results following non-operative treatment for fracture of the neck of the fifth metacarpal

AIM

To investigate in fractures of the fifth metacarpal neck whether there is any difference in functional results of non-operative treatments with dorsal angulation either below or above 30 degrees.

METHODS

After closed reduction, fractures were treated with plaster splints for 5 weeks. Cases were divided into two groups, with dorsal angulation either below (group 1) or above (group 2) 30 degrees, according to oblique radiography, and were evaluated at 6 months. Grip strength, range of passive joint movement and distance from fingertip to distal crease were measured and compared. A scoring system assessed function, and occupational adequacy, patient satisfaction and presence of pain were recorded.

RESULTS

Functional outcome was good or very good in both groups and occupational adequacy was not reduced in any case. Full patient satisfaction was achieved except for one person in group 1 and two people in group 2, regarding cosmetic results. There was no statistically significant difference between the two hands in either group except for one man from group 2, who had mild pain during coercive use of the injured hand.

CONCLUSIONS

With non-operative treatment of fractures of the neck of the fifth metacarpal, similar results were achieved with dorsal angulation either above or below 30 degrees. A dorsal angulation less than 45 degrees may be treated conservatively.

Behavior of an Up-flow Anaerobic Sludge Bed (UASB) reactor at extreme salinity

High salinity is one of the most well known inhibitors and salt concentrations above 1% are reported as highly saline. Salt may be found in the main collectors of municipal sewer systems which carry the risk of seawater infiltration and where domestic wastewaters are treated with landfill leachates such cases in Istanbul. Discharging of leachates into sewerage would also result in additional ammonium loads in Municipal Treatment Plants (MTPs). In this study, synthetic wastewater was fed to a lab-scale Upflow Anaerobic Sludge Bed (UASB) reactor operated at a constant hydraulic retention time (HRT) of 1 day. The salt concentration was increased artificially whereas the ammonium concentration was fixed at 1000 mg/l throughout the study. Results indicated no significant inhibition up to 2% salinity + 1000 mg/l NH4 and TOC removals could reach up to 88%. Besides, effective total biogas productions having methane content of 84% could be achieved. It is obvious that anaerobic microorganisms (especially methanogens) could well adapt to high salinity ratios. No inhibition at high ammonium concentration might have been attributed to the fact that the pH in the system was not high enough for the formation of free ammonia. Investigation of the combined effect of high salinity and ammonium was carried on by increasing the salinity to 3% in the study. Results indicated that TOC removals decreased to around 56% and 3% salinity caused . a sharp decrease both in organic material removal and total biogas production. Thus the critical salinity level was determined as 3% for the methanogens in the mesophilic anaerobic digesters.

Effect of high salinity on anaerobic treatment of low strength effluents

In anaerobic treatment, it is obligatory to know the effect of potentially inhibitory compounds due to the fact that methane formation may retard severely and may proceed slower than organic acid production. One of the most important inhibitory substances in anaerobic treatment is high salinity. In many cases, the main collectors of a municipal sewer system should have been built in the coastal zone and below the ground water level due to the available topography of wastewater catchments area, which is carrying the risk of seawater infiltration. Besides, one of the most convenient methods for leachate control is to treat landfill leachates with domestic wastewaters in the central municipal wastewater treatment plants such as in Istanbul. Thus, the nitrogen load of the treatment plants increase significantly. In this study, the effects of high salinity and ammonium nitrogen levels on mesophilic anaerobic tretament processes were investigated. In the first part of the study, high salinity effect on anaerobic treatment was investigated by feeding synthetic wastewater containing high salinity between 0.15%-1.5% ratios. In the second part of the study, the simultaneous effect of high salinity and ammonia (1.5% salinity+1,000 mg NH3/l) was examined by a lab-scale Upflow Anaerobic Sludge Bed Reactor (UASBR). Results indicated no significant inhibition in both cases and effective COD removals (89%) and total biogas productions having methane content of 84% could be achieved.

Investigation of variations in microbial diversity in anaerobic reactors treating landfill leachate

A young landfill leachate containing elevated total ammonia concentrations frequently as high as 2,700 mg/l was anaerobically treated for 1,015 days in two different laboratory-scale anaerobic reactors configured as sludge blanket and hybrid bed. In this paper, the last 265 days of this long-term anaerobic treatability study are presented. Effects of high ammonia concentrations on reactor performances were correlated to the variations in microbial diversity by identifying the dominant microorganisms with FISH (fluorescent in-situ hybridization), cloning, DGGE (denaturing gradient gel electrophoresis) and morphological analysis. The results have indicated that the high ammonia landfill leachate can be treated successfully by using either an UASB or a hybrid bed reactor if temporary pH adjustments in the reactor influents are made when high ammonia concentrations are experienced. Consequently, COD removal efficiency is independent of microbial diversity and reactor configuration and it depends on the biodegradable portion of the leachate. Under this circumstance, stability of the reactors with low levels of acetate was supported by the abundance of Methanosaeta population. In both of the reactors, some populations of Methanobacteriaceae were also detected while other methanogenic species were virtually absent. However, after the termination of pH adjustment at Day 860, reactors immediately became unstable due to the sudden increase in free ammonia concentration up to 400 mg/l. COD removal efficiency decreased to 42% in the hybrid bed and to 48% in the UASB reactor. The durations of inhibitions were not long enough to severely deteriorate the massive Methanosaeta cells; therefore, many of them were again identified after two free ammonia inhibitions. However, subsequently, long filamentous morphologies of Methanosaeta cells shifted to shorter filaments and they lost their aggregating property.

Struvite precipitation from anaerobically treated municipal and landfill wastewaters

A two-stage treatment system including upflow anaerobic sludge blanket reactor pre-treatment combined with a chemical post treatment system such as magnesium ammonium phosphate (MAP) precipitation was proposed as a comparable alternative to conventional biological treatment. In this study, anaerobically pre-treated domestic wastewater, domestic wastewater mixed with 2% and 3% of leachate by volume and raw leachate were further treated chemically with MAP precipitation. MAP precipitation was both applied at the stoichiometric ratio (Mg:NH4=PO4; 1:1:1) and above the stoichiometric ratio (1.1:1:1 and 1.1:1:1.1) on domestic wastewater + 3% leachate mixture. Maximum NH4-N removal of 68% was achieved at the pH of 9.2 at the stoichiometric ratio, whereas at the same pH value 70 to 72% NH4-N removal was obtained above the stoichiometric ratio. Additional ammonia recovery studies were conducted on Fenton's oxidation applied effluents before MAP precipitation and no significant additional ammonium removal was achieved. However, by the application of Fenton's oxidation high additional COD removals were obtained. Consequently, chemical treatment by MAP precipitation and/or Fenton's oxidation after anaerobic treatment yielded very effective removals for COD and NH4-N in domestic wastewaters + leachate mixtures.

Ammonia recovery from high strength agro industry effluents

The aim of the study was to investigate ammonia recovery from high strength agro industry effluents involving significant amounts of ammonia, by applying magnesium ammonium phosphate (MAP) precipitation technology. Two types of industrial effluents have been tested in the study. The first plant was an opium alkaloid processing industry and the second one was a baker's yeast industry. High chemical oxygen demand (COD), total Kjeldahl nitrogen (TKN) and unacceptable dark brown color characterized effluents from both industries. Effluents from the biologically treated opium alkaloid and baker's yeast industries were both applied at the stoichiometric ratio (Mg:NH4:PO4 = 1:1:1) and above the stoichiometric ratio (Mg:NH4:PO4 = 1.1:1:1.1) to MAP precipitation. NH4 removals of 61-80% were achieved at the pH of 9.2 at the stoichiometric ratio, whereas 83% NH4 removal was obtained at the pH of 9.2 above the stoichiometric ratio. Experimental studies performed on both anaerobically and/or aerobically treated baker's yeast and opium alkaloid industry effluents have clearly indicated that MAP precipitation was an appropriate treatment option for NH4 removal or struvite recovery from high ammonia content agro industry effluents. Additional ammonia recovery studies were conducted on ozonated and Fenton's oxidation applied effluents and these have also indicated that the amounts of struvite and the quality of MAP precipitate was increased significantly. In this framework, MAP sludge recovered from combined biological and Fenton's oxidation treatment effluents were considered as a more valuable slow release fertilizer for agricultural use.

Toxicity assessment on combined biological treatment of pharmaceutical industry effluents

This paper describes the wastewater characterization and aerobic/anaerobic treatability (oxygen uptake rate and biogas production measurement) of chemical-synthesis based pharmaceutical industry effluents in a nearby baker's yeast industry treatment plant. Preliminary experiments by the industry had indicated strong anaerobic toxicity. On the other hand, aerobic treatability was also uncertain due to complexity and unknown composition of the wastewater. The work in this study has indicated that the effluents of the pharmaceutical industry can be treated without toxicity in the aerobic stage of the treatment plant. Methanogenic activity tests with anaerobic sludge from the anaerobic treatment stage of the wastewater treatment plant and acetate as substrate have confirmed the strong toxicity, while showing that 30 min aeration or coagulation with an alum dose of 300 mg/l is sufficient for reducing the toxicity almost completely. Powdered activated carbon, lime and ferric chloride (100-1,000 mg/l) had no effect on reduction of the toxicity. Consequently, the pharmaceutical industry was recommended to treat its effluents in the anaerobic stage of the nearby baker's yeast industry wastewater treatment plan at which there will be no VOC emission and toxicity problem, provided that pretreatment is done.

Advanced treatment of high strength opium alkaloid industry effluents

The purpose of this study was to investigate an effective treatment system which can be applicable to treat opium alkaloid industry (OAI) effluents characterised with high COD, TKN, dark color and non-biodegradable organic pollutants. In the first phase of the study, lab-scale anaerobic (UASBR) + aerobic (SBR) treatability studies were carried out on opium processing industry effluents. Effluent CODs from the two staged biological treatment system were relatively high (-700 mg l(-1)) and additional post treatment was required. Physico-chemical treatability studies previously carried out on the effluent of opium alkaloid wastewater treatment plant, were not effective in removing residual COD and color. In the second phase of the study, the refractory organics causing higher inert COD values in the SBR effluent were additionally treated by using Fenton's Oxidation. The batch tests were performed to determine the optimum operating conditions including pH, H2O2 dosage, molar ratio of Fe2+/H2O2 and reaction time. It was found that removal efficiencies of COD and color for 30 minutes reaction time were about 90% and 95%, respectively. The ratio of H2O2/FeSO4 was determined as 200 mg l(-1)/600 mg l(-1) for the optimum oxidation and coagulation process at pH 4. Experimental results of the present study have clearly indicated that the Fenton's oxidation technology is capable to treat almost all parts of the organics which consist of both soluble initial and microbial inert fractions of COD for opium alkaloid industry effluents. Effluents from the Fenton's Oxidation process can satisfy effluent standards for COD and color in general.

A new process for the combined treatment of municipal wastewaters and landfill leachates in coastal areas

One of the most convenient methods for leachate control is to treat landfill leachates with domestic wastewaters. In this framework, a two-stage treatment system including anaerobic pre-treatment combined with a chemical post-treatment system such as ammonia stripping and/or Magnesium Ammonium Phosphate (MAP) precipitation can be comparable with a conventional secondary biological treatment. In this study, 2.5% and 2% of leachate by volume was mixed with domestic wastewater as the feed for the mesophilic Upflow Anaerobic Sludge Bed Reactor (UASBR). pH, feed strength and hydraulic retention time (HRT) were monitored for the evaluation of the performance of the anaerobic process. The HRT's varied from 0.76 to 0.52 d and 58% and 85% COD removal efficiencies were obtained at Organic Loading Rates (OLR) of 0.63 and 2 kg COD/m3.d respectively. The average biomass (VS) concentration in the reactor increased from 40 g/l to 50 g/l during the study. Effluents from the UASBR were further treated chemically either with lime for ammonia stripping or with MAP precipitation. MAP precipitation was applied both at the stoichiometric ratio (Mg:NH4:PO4 = 1:1:1) and above the stoichiometric ratio (Mg:NH4:PO4 = 1:1:1.3). Maximum NH4 removal of 66% was achieved at the pH of 9.3 at the stoichiometric ratio, whereas 86% NH4 removal was obtained at the pH of 9.3 above the stoichiometric ratio. Alternatively, ammonia stripping was applied either to the effluents directly taken from the anaerobic reactor or to the effluents to which MAP precipitation was applied stoichiometrically. Ammonia stripping was conducted for 24 h and 89% NH4 removal was observed at the end of 24 h. Consequently, this study indicates that anaerobic pre-treatment combined with chemical post-treatment (MAP) produced high quality of effluent comparable to the conventional biological treatment especially in terms of N and P levels.

Influence of different bioparticles on bed expansion characteristics of anaerobic fluidized bed reactors

Bed expansion characteristics and predicting biofilm development and biomass hold-up in the anaerobic fluidized bed reactor were investigated. The treatability studies of brewery wastes were carried out in a pilot-scale fluidized bed reactor for a nine months period. The expansion and particle mixing characteristics of a fluidized bed containing different bioparticles is a complicated function of many variables, including hydrodynamics, support characteristics, and biofilm structures. The biological fluidized bed reactors have two types of bed expansion; the first is due to an increase of the superficial velocity and the second is due to the microbial growth in the bed. A new relationship for the porosity of the biological fluidized beds, was developed. Biofilm thickness and bed porosity increased rapidly in the upper part of the bed and the bioparticles become lighter than the clean particles with decreasing effective density. Most bioparticles in the anaerobic fluidized bed reactor (AFBR) were ellipsoidal and the geometric mean diameters were considered as the characteristic diameter. Their surface roughness causes an increase in the drag force acting on the particle. Thus, the expansion coefficient increased from 3.44 to 3.64 as terminal settling velocity decreased from 6.99 to 4.29 cm/s. An almost linear relationship was observed between local porosity and biofilm thickness. The differences between the measured and calculated biomass concentrations varied in the range of 0.4 and 12% (average 4.6%) considering the results from the pilot-scale AFBR. The bed expansion rate of the AFBR, varied from 12.3 to 18.3% whereas, the expansion rate of the clean bed also found between 7.9 and 12.7%. Consequently, the bed expansion rate due to biofilm accumulation on the particles can be well described to vary between 4.4 and 5.6%.

Application of membrane and ozonation technologies to remove color from agro-industry effluents

The results of membrane and ozonation experiments carried out on various agro-industry effluents including fermentation (baker's yeast), corrugated board, opium alkaloid and textile dying industries are presented. The experiments were performed using lab-scale membrane and ozonation reactors. Color removals were in the range of 80 to 99% for the membrane treatment studies. Ozonation experiments have shown that color removals in the range of 83 to 98% are possible for the investigated wastewaters. Final color levels were lower than 100 Pt-Co unit, which is quite acceptable aesthetically. The relative unit treatment costs of ozonation were about two times higher than membrane systems especially for very strong colored effluents including fermentation and opium alkaloid industries. The study has demonstrated that both membrane and ozonation technologies are viable options for color removal.

Avascular necrosis of the femoral head in childhood: the results of treatment with articulated distraction method

The treatment of avascular necrosis of the femoral head in children is still being debated. We performed articulated distraction in 11 children with avascular necrosis of the femoral head between March 1994 and February 1997. The reasons for avascular necrosis were: Perthes disease in eight patients, fracture of the femoral neck in two, and complication arising because of treatment of developmental hip dysplasia in one. Mean age was 7.9 years. Fixator duration time was 3.5 months and mean follow-up was 32 months. At follow-up, the femoral head was spherical and congruent in four patients, aspherical and congruent in five, and aspherical and incongruent in two according to Stulberg's criteria. The aim of the articulated distraction method is to neutralize muscle and weight-bearing forces, to prevent stress fractures of subchondral immature bone, to encourage synovial circulation, and to promote creeping substitution.